Earth moving machine with depth and cross-shape controls

ABSTRACT

This invention relates to the control of the height or cross slope or both of an earth working tool such as a scraper blade with height control achieved by use of an external elongated reference member disposed along the path to be traveled by the scraper to actuate the hydraulic control valve of a ram used to move the earth working tool. A pendulum-actuated control valve is used to control cross slope disposition.

United States Patent Inventors John Curlett Los Gatos; Raymond A. Gurries, San Jose, Calif. Appl. No. 852,997 Filed Aug. 25, 1969 Patented Feb. 9, 1971 Assignee Gurries Manufacturing Co. San Jose, Calif., aggrporation of California Continuatidn of appliFItiBn er. No. 758,645, Aug. 15, 1968, now abandoned which is a continuation-in-part of application Ser. No. 339,069, Jan. 13, 1964, now abandoned which is a continuation-in-partof application Ser. No. 157,407, Dec. 6, 1961, now abandoned.

EARTH MOVING MACHINE WITH DEPTH AND CROSS-SLOPE CONTROLS 1 Claim, 10 Drawing Figs.

08. Cl l72/4.5, 37/1 18, 37/126;172/23, 172/798 Int. Cl E021 3/76, 1202f 3/00 [50] Field of Search 37/108, 118, 124, 126A1 A5, 129, (AL), (SAL), (A.C.);

[56] References Cited UNITED STATES PATENTS Primary Examiner-Robert E. Pulfrey Assistant Examiner-Eugene H. Eickholt Attorney-Paul B. Fihe ABSTRACT: This invention relates to the control of the height or cross slope or both of an earth working tool such as a scraper blade with height control achieved by use of an external elongated reference member disposed along the path to be traveled by the scraper to actuate the hydraulic control valve of a ram used to move the earth working tool. A pendulum-actuated control valve is used to control cross slope disposition.

EARTH MOVING MACHINE WITH DEPTH AND CROSS- P9IEQ This application is a continuat ibmdf pfiFc zop efihg application, Ser. No. 758645, filed 8/ /68, now abandoned, which in turn was a continuation of copending application, Ser No. 339069, filed 1/13/64, now abandoned, which in turn was a continuation of copending application Ser. No. 157,407, filed 12/6/61, now abandoned.

This invention relates to the type of earth moving machines commonly known as scrapers in which the working edge of an earth working tool such as a blade scrapes the ground, and more particularly to control means for automatically maintaining the height or cross slope or both of the working edge of the blade of a carry type or blade loading scraper in relation to a selected reference.

Generally speaking, a scraper comprises a main frame which has the earth working blade rigidly affixed thereto and which is supported on ground support means such as wheels. The height of the blade is controlled by raising and lowering the main frame with respect to the ground support means. For this reason adjustable supports including hydraulically operated rams are utilized between the main frame and either the rear or the front ground support means.

In many types of scrapers, such as the carry type or blade loading scraper, the earth worked by theblade is deposited into an earth carrying bowl affixed to the main frame for removal at a later time. The function of the typical scraper is to scrape or work the earth, to load the excess loose earth into the bowl and to transport the loose earth elsewhere for unloading. In other words, many scrapers known today, in addition to scraping, also load, transport and unload the earth so dug up. This invention relates primarily to the cutting and spreading operations of the scraper and may be utilized with conventional scrapers without affecting the carrying or any other manually controlled operation.

Heretofore, height adjustment of the blade was accomplished by manually operating hydraulic valves which injected or removed hydraulic fluid under pressure to or from the hydraulic rams which connected the main frame to the ground support or ground traction means. Manual control necessitated constant vigilance by a skilled operator who had to judge, as best he could, whether the desired grade was cut by the scraper. Means for controlling cross slope of the scraper blade, as far as could be ascertained, have been unknown.

The cut made by' conventional scrapers was therefore rough and depended as far as grade was concerned, entirely on the skill of the operator. As a consequence of the very rough approximation to the desired grade and the impossibility of con trolling the cross grade, the scraper had to be repeatedly used until the desired contour was finally achieved. Particularly in the building of roads, ditches and the like, the scraper was useful only in providing a very rough approximation of the desired road or ditch bed necessitating further cutting operation with expensive automatic roadbuilding machines in order to properly grade and cross grade the road bed for the next operation.

It is therefore one object of this invention to provide earth working equipment capable of making a cut having the desired grade and cross grade and thereby obviating the necessity of fine scraping. I g

It is a further object of this invention to provide a vastly more versatile blade loading scraper then heretofore known which eliminates the need for manual operation for the adjustment of blade height of the cutting blade, thereby saving skilled manpower and which furthermore provides a' cut having the desired grade and cross grade.

It is another object of this invention to provide a scraper whose blade height is automatically controllable by a lever guide such as a grade wire or grade surface set to the desired grade.

It is another object of this invention to provide a scraper whose blade has its cross slope controlled to provide a cut having a desired cross grade.

It is a further object of this invention to provide a scraper in which the grade and the cross grade of the cutto be scraped is controlled by some level guide and by a cross slope control means to provide automatic control of both grade and cross grade.

It is still another object of this invention to provide a scraper which includes automatic leveling mechanism which maintains the cutting edge of the blade, during its advance, at a predetermined and absolutely accurate level regardless of any variation of the level of the ground to be traversed and which provides a cross level control means which is also independent of any variation of the ground.

In accordance with the preferred embodiment of the scraper of this invention, one or more hydraulically adjustable rams are utilized to support the forward portion of the main frame with respect to the forward ground support means. The hydraulic rams (if more than one) are connected to a common hydraulic control valve whose valve actuating member is actuated either directly or indirectly by engagement with a level guide such as a grade wire or a preformed slab placed along the path of the scraper. As a result of the engagement of the valve actuating member with the level guide, hydraulic fluid is forced into or removed from the rams whenever the cutting edge of the blade moves lower or higher in relation to the grade set by the level guide.

Cross grade control is provided by controlling the cross grade of the plane of the main frame relative to the ground support means supporting the scrapeLTo this end, a hydraulically operated ram may be interposed between the main frame and one of the rear ground support means, or the rear axle engaging the ground support means may be split and a hydraulic ram utilized together with levers to differentially adjust the respective height of the split rear axles and thereby the plane of the main frame. The hydraulically operated ram is controlled by a pendulum (gravity) operated valve which automatically maintains the desired cross grade of the main frame independent of the cross grade of the ground.

Other objects and a fuller understanding of the invention may be had by reference to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. I is a side elevational view of the scraper of this invention;

FIG. 2 shows a partial top view of the scraper of FIG. I, certain conventional parts of the superstructure having been omitted for the sake of clarity;

FIG. 3 is an enlarged sectional top view of the automatic grade leveling means of FIG. 1;

FIG. 4 is a side elevational view of the grade leveling means shown in FIG. 3;

FIG. 5 is a schematic hydraulic flow diagram of the automatic grade leveling means for adjusting blade height, including also the necessary controls for manual operation;

FIG. 6 is a rear view of the scraper of FIG. 1, showing further details of the automatic cross grade control means;

FIG. 7 is a schematic hydraulic flow diaphragm of the cross grade control of the scraper of FIG. 1;

FIG. 8 is a rear view, just like FIG. 6, showing a still further embodiment of the cross grade control means;

FIG. 9 is a partial top view of the cross grade control means of the embodiment shown in FIG. 8; and

FIG. 10 is a schematic flow diagram of the cross grade control utilized in connection with the scraper of FIG. 8.

Referring now to the drawings, in which like reference characters designate like parts, and particularly to FIGS. I, 2, and 5 thereof, there is shown a scraper designated generally by reference character 10. Scraper 10 comprises a main frame 12 which includes a main member 13 to which cross members 14 and peripheral members 15 are attached. An earth working blade 18 is firmly fastened to peripheral member 15. Main frame 12 is also provided with side, bottom and back plates 20 which form the bowl or bucket into which excess earth is deposited for later removal to a dump or an area to be filled in.

Main frame 12 is supported rearwardly by a pair of ground engagement means such as wheels 22 and 23. in one embodiment of this invention, right rear wheel 23 is joumaled in a pair of rigid brackets 24 and 25 fixedly attached to and rearwardly and outwardly depending from main frame i2. Brackets 2 1 and 25 may comprise a pair of horizontal bars having bearings in their end portions engaging the wheel axle 26. For additional support a pair of angularly spaced braces 27 and 28 may be utilized which are fastened to the rear portion of peripheral member 115.

The left rear wheel 22 is likewise joumaled in a pair of brackets 30 and 31 but brackets 38 and 31 are pivotably connected to main frame 12 so that the associated side (left side) of main frame 12 may be lowered or raised. A hydraulically operated ram 32 forms an angular bracket between main frame 112 and the outwardly depending end portion of bracket 3i whose length is hydraulically adjustable. By forcing hydraulic fluid into ram 32, its length increases and thereby lowers the end portions of brackets 30 and fill which support wheel axle 33. Since wheel 33 is in intimate contact with the ground, and therefore cannot be further lowered, the expansion of ram 32 raises the left side of main frame 12 thereby changing the cross slope (grade) of main frame 12 and blade 323.

Even though ram 32 has been described as being connected to bracket 31, it is of course immediately obvious to those skilled in the art that the dependent cylinder or plunger 34 may be connected to the arm of a yoke whose U-shaped end is joumaling wheel axle 33. Many arrangements to provide a wheel support capable of raising and lowering main frame 112 with respect to wheel axle 33 with the aid of a ram whose length is adjustable are known and may be utilized to practice this invention.

The forward end of main frame 112 is supported by a pair of ground engagement means such as wheels of which only wheel 40 is shown. Front wheels 430 are connected to one another by front wheel axle it which also pivotably supports a draw bar 412 which may be connected to a tractor (not shown) which provides the motive power to scraper 10 in the customary manner. Connecting main frame 112 and front wheels 40 is a conventional yoke 42 having a gooseneck 33 journaled to front wheel axle 41 either directly or through a universal 43 to permit main frame 112 to assume a desired cross slope as will be explained hereinafter. The yoke arms 44 (only one of which is shown) depending from yoke cross member 45 are pivotably connected to main member 13 by means of pivot supports as holding pivot pin 47.

A pair of hydraulically operated rams 48 and 49 (see FIG. connect the front end portions of main member B3 to yoke cross member 45 by means of brackets 58 and 51. Rams i8 and 459 are preferably operated in parallel, as will be explained, and upon contraction raise the front end of main frame 32 and thereby blade 18. Instead of utilizing two rams such as rams $8 and 49, it is also within the contemplation of this invention that a single hydraulically operated ram may be utilized to raise and lower the front end of main frame 112. For example, bracket 56 and the corresponding bracket on the right side of scraper 118 may be tied together and a single ram connected thereto and to the central portion of cross arm 45. Also, the central yoke arm of a further yoke may be tied via a ram to cross arm 45 and the two side arms of the further yoke may engage opposite main members 13 as is well known in the scraper construction art.

Grade control of scraper 1 .8 is provided by grade leveling means 68 for actuating a valve 611 which is connected to a hydraulic system 62 which in turn controls rams 48 and 49. When hydraulic fluid under pressure is injected into hydraulic lines 841, the dependent cylinders of double-acting rams 48 and w will be forced upward and thereby raise main frame 12. Conversely, application of hydraulic fluid to line as will lower the dependent cylinders and thereby lower main frame 32 and thereby blade 18. Cross grade control of scraper 118 is provided by a pendulum operated valve of which control hydraulic operated ram 32 and which, upon contraction and expansion, tilts the main frame as will be explained in connection with the description of FIGS. 6 and 7.

Referring now to the automatic leveling means of FIGS. 3 and 4, a pair of U-shaped support brackets 70 and 71 have their center portions firmly bolted to main member 13 so that their end portions 72 and 73 depend outwardly in parallel relationship toward each other. A pair of guide bars 74 and 75 preferably of cylindrical cross section are firmly held at their respective end portions by the extremities of the outwardly depending portions of support brackets 70 and 71 in such a manner that guide bars 74 and 75 are parallel to one another.

Guide bars 74 and 75 provide a vertically adjustable support for a support plate '76 which includes a pair of end bosses containing cylindrical bores dimensioned for sliding engagement with guide bars 7 and 75. To clamp support plate 76 at a desired vertical position to guide bars 74 and 75, set screws 77 may be provided in each boss in the customary manner.

Support plate 76 provides an adjustable support for a hydraulic valve means such as a fourway closed-center valve 611 and the leveling means for actuating valve 61. For purposes of illustration, two leveling means are shown, one being a wire fork 79 engaging a stake supported grade-wire 80 and the other being a gauge wheel 81 in contact with a preformed slab or a roadway 82. It is to be understood that either one of these leveling means may be used without the other and that showing both such leveling means incorporated with the scraper of this invention is only a preferred embodiment providing additional versatility so that one or the other mode of leveling may be selected in accordance with the best and least expensive mode of operation depending on the nature and the environmental conditions encountered on the job.

Valve 61 is provided with a valve actuating member 84 which actuates hydraulic fluid flow when rotated about its axis from some neutral angular position. Connected to actuating member 84 is a horizontally extending arm 85 to which wire fork 79 such as described in copending application Ser. No. 108,902, filed May 9, 1961 is removably connected. Support plate 76 is also provided with a pair of support bosses 86 and 87 which form a surface to which a pair of arms 88 and 89 are pivotably connected. Arm 88 has connected to its lower end portion, gauge wheel 81 preferably by means of a bearing so it may freely rotate about its axis. Arm 89 is provided with an extended closed slot 90 which slidingly engages a pin 91 securely fastened to arm 88. A rod 92 detachably connects arm 88 to horizontally extending arm 85 to transmit any motion of arm 88 about its pivot support 93 to valve actuating member 84.

The vertical height of support plate 76 is adjusted in such a manner that as gauge wheel 81 engages level surface (or wire fork 79 engages grade-wire 80) valve actuating member 84 is in its neutral angular position when blade 18 is at the desired height. Since the blade moves up and down with main frame 12, any variation of the cutting edge of blade 18 from the desired height will be transmitted, via angular motion of arm 88 about pivot point 93, connecting arm 92 and arm 85 (and in case of a wire fork directly to arm 85) to valve actuating member 84. Elongated slot engaging pin 91 sets the limit of angular motion of arm 88 so that when main frame 12 is raised for turning the scraper or carrying or dumping the earth, arm 88 is supported by arm 89 and no mechanical stress is placed on valve actuating member 84. As will be explained in connection with the description of FIG. 5, valve 61 will actuate hydraulic arms 48 and 49 to bring main frame 112 and thereby blade 18 back to the desired height.

Referring now to FIG. 5, there is shown a schematic hydraulic system (block 62, FIG. 1) which may be used in connection with the grade leveling system of the blade in accordance with this invention. Basically, the hydraulic system comprises an interlocked manual and an automatic control system, the manual control being provided by valve and the automatic control being provided by valve 61. The hydraulic fluid system for operating the automatic leveling system includes an hydraulic fluid tank 1101 for holding hydraulic fluid, a pump 102 connected thereto to develop hydraulic pressure, a conventional constant pressure regulator 103 connected to pump 102, and a bypass line across tank 101, pump 102 and regulator 103 through conventional heat exchanger 104 which provides! cooling for the hydraulic fluid in the hydraulic fluid system. Tank 101, pump 102, regulator 103 and heat exchanger 104 therefore define a constant hydraulic fluid pressure system which supplies hydraulic fluid under constant pressure to hydraulic high pressure |ine105. If the pressure developed by pump 102 exceeds a predetermined pressure, regulator 103 opens a bypass port permitting fluid to circulate back to tank 101 through the bypass line.

Hydraulic high pressure line 105 is connected to the input port of four-way closed center valve 61 which is also provided with a return low pressure hydraulic line 106 connected to the tank 101. Valve 61 has two hydraulic output lines 107 and 108 respectively connected to both inputs ports of double acting hydraulic rams 48 and 49 through a pair of three way selector valves 109 and 110. As will be explained hereinafter, selector valves 109 and 110 are switched from one position to another between automatic and manual operation. In the position shown in FIG. 5, selector valves 109 and 110 are shown in an automatic control position in which lines 107 and 108 are respectively connected to lines 64 and 65.

In operation, wire fork 79 held by arm 85 engages gradewire 80 (or rod 92 through arm 88 and wheel 81 engages slab 82) and turns actuating element 84 whenever main frame 12 deviates from the reference height set by grade-wire 80. Rotating motion of valve actuating element 84 from a neutral usually horizontal position in either direction causes communication between high pressure hydraulic line 105, low pressure hydraulic line 106 and lines 107 and 108 in the following manner. When main frame 12 is below the reference grade set by grade-wire 80, wire fork 79 moves upward and connects high pressure line 105 to line 64 to cause injection of hydraulic fluid under high pressure into the dependent cylinders of rams 48 and 49 to shorten the rams and thereby raise main frame 12 until wire fork 79 again assumes a neutral position. At the same time low pressure line 106 is connected to line 65 to permit the removal of hydraulic fluid from the upper portions of rams 48 and 49. When main frame 12 is to be lowered, lines 105 and 106 are communicated with lines 65 and 64 respectively.

Valve 61 is preferably selected of the type having a closed center so that no hydraulic fluid is circulated if actuating element 84 is in its neutral position. The reason for this choice is that a closed center valve is capable of greater sensitivity since a small displacement of the valve element provides the desired communication with lines 64 and 65. Of course an open center valve may also be used in place of valve 61 but considerably more travel of the valve element is required since the center must be closed prior to establishing the necessary communication with lines 64 and 65. Also other modifications may be made such as replacing double acting cylinder rams with single acting cylinder rams.

Tank 101 is also connected to a second pump 114 which in turn is connected via a further highpressure hydraulic line 115 to the manual valve 100 which may be a four-way open center valve and which consequently circulates hydraulic fluid back to take 101 via line 1 16 as long as the valve element is in a neutral position. Valve 100 is likewise connected to selector valve 109 and 110 via lines 117 and 118. In order to make certain that the blade level control is being controlled either by manual or by automatic operation, but not by both at the same time (the automatic control always wanting to override the manual control), two selector valves 109 and 110 and the switch of manual control valve 100 are ganged in such a way' that operation of the manual control valve handle 119 immediately switches selector valves 109 and 110 to connect lines 64 and 65 to lines 118 and 1 17 respectively.

Operation of. the manual control system is similar to that described in connection with the automatic control system except that lines 107 and 108 are exchanged for lines 117 and 118. In order to manually raise main frame 12, valve handle 119 is for example pushed downwards which causes the valve element of valve to close the center and establish communication between high pressure line and line 64. At the same time low pressure of return line 116 is communicated with line 65. If main frame 12 is to be lowered lines 64 and 65 are reversed.

As previously indicated, cross grade controlis provided by utilizing a pendulum controlled servo valve 66 mounted upon main frame 12. Valve 66 may take a number of different forms but basically comprises a pair of flow passages for intake and return and one or more outlet passages which are selectively connected to the flow passage in accordance with the position of a valve actuating element. The position of the valve actuating element in valve 66 is controlled by a gravity operated pendulum so that any deviation from a neutral position (neutral cross grade) moves the valve actuating element to communicate the proper flow passage with the outlet passage to reduce the deviation to zero. This valve is fully described in US. Pat. No. 2,934,078 entitled Pendulum Controlled Valve".

Referring now to FIGS. 6 and 7, there is shown an embodiment of the cross grade control utilized in connection with scraper 10. As has already been explained, hydraulically actuated ram 32 controls the cross slope of main frame 12. As dependent cylinder 34 moves out of ram 32, the left side of main frame 12 moves up thereby tilting blade 18 to the proper cross slope.

Valve 66 is connected to a constant hydraulic fluid pressure system 120 which may comprise the system shown in FIG. 7 including a tank, pump, regulator and a heat exchanger in a bypass line. Connections are made via high pressure line 121 and return or low pressure line 122. Valve 66 is preferably selected to be a three-way closed center valve so that a slight movement of the valve element will communicate either high pressure line 121 or low pressure line 122 with hydraulic line 123 which controls hydraulic ram 32. A valve, such as twoway selector valve 124 may be interposed between valve 66 and ram 32 to close this connection when it is desired to disconnect the cross slope control system. Upon closing valve 124, ram 32 remains in the state of extension determined by the fluid left in there.

Operation of valve 66 is asfollows: Valve 66 is adjusted by dial 125 to a desired neutral position, that is if a cross grade of say 5 is desired, the valve actuating element in valve 66 remains in its. neutral position as long as main frame 12 is inclined 5. Any deviation from this 5 inclination is immediately sensed by valve 66 and hydraulic fluid is injected into or removed from ram 32 until main frame 12 again assumes the 5 cross slope.

In the embodiment shown in FIG. 6, wheels 22 and 23 are positioned inwards from the sides of scraper 10 and since blade 18 usually extends all the way across scraper 10, wheels 22 and 23 engage the scraped path. As a result of placing the rear ground engagement means inside the scraped path, main frame 12 will remain parallel with the axis of wheels 22 and 23 so that for any desired cross slope the extension of ram 32 is the same. The extension of ram 32 only changes in order to correct the cross grade and assumes its normal extension as soon as the proper cross grade is reestablished. The advantages of such a system is that a relatively short stroked type of ram may be employed since, except for correcting errors, its length remains fixed.

Of course, the cross grade control may likewise be utilized in connection with scrapers whose rear wheels are riding on the ground outside the blade worked strip. The major difference is that main frame 12 will usually not be parallel to the rear wheel axles and consequently a ram having a relatively longer stroke is necessary so that a desirable tilt with respect to the ground contour may be achieved. In this instance different cross slopes over the same course require a different degree of ram extension.

A different embodiment of the cross grade control of the scraper constructed in accordance with this invention is shown in FIGS. 8 and 9. As there shown, the rearward end 170 of main frame of the scraper is provided with a support 171 about which is joumaled a rocker or rear wheel axle housing 172. Opposite'extremities of rocker 172 are provided with rear axles 173 and 174 about which rear wheels 1175 and 176 are respectively joumaled. Also attached to rearward end 170 of the main frame is a support structure generally indicated by reference numeral 177. Rocker arm 178 of rocker 172 is connected to support structure 177 by means of hydraulically controlled ram 179.

In operation ram 179 is controlled by a pendulum operated servo valve in much the same manner as explained in connection with the description of FIG. 7. As ram 179 extends it moves rocker arm 178 to the right and thereby tilts rocker 172 and thereby the main frame of the scraper. In this embodiment is also preferable to use a double-acting piston for ram 179 since both contraction and expansion must be accomplished by the injection of hydraulic fluid at high pressure.

FIG. is a hydraulic diagram similar to the one shown in FIG. 7 except that it shows actuation of a double-acting cylinder. Accordingly, a pendulum operated servo valve of the closed center four-way type is selected for valve 182 and has applied thereto hydraulic fluid under pressure via line 183. A return hydraulic line is provided by line 184 and both outlet lines 185 and 186 are connected to respective ends of doubleacting pistons 187. A pair of gang two-way selector valves 188 and 189 are respectively inserted into lines 185 and 186. Closing of selector valves 188 and 189 will disconnect ram 187 from the control of the pendulum operated valve 182 keeping the degree of extension of ram 187 constant since fluid can neither enter nor leave either end of the cylinder.

There has been described a scraper having automatic level and cross level control. The level reference is provided by a grade wire or surface along the path the scraper is to traverse and the cross level reference is provided by a pendulum operated servo valve. Raising and lowering of the blade is accomplished by utilizing two hydraulic rams connected in parallel to further allow tilting of the main frame. When the frame is tilted by the automatic cross slope control, fluid is interchanged between the rams controlling the blade height.

We claim:

1. A blade loading scraper comprising:

a main frame,

an earth working blade supported on said frame,

rear traction means supporting the rear portion of said frame,

a yoke having a pair of rearwardly extending side arms pivotally connected to an intermediate portion of said frame,

front traction means supporting the forward end of said yoke,

a double acting hydraulic ram connected between the intermediate portion of said yoke and the forward portion of said frame for controlling the elevation of said main frame,

first and second flow lines communicating with opposite ends of said hydraulic ram,

first and second three-way selector valves in continuous communication with said first and second flow lines respectively,

a first automatic control fluid line and a first manual control fluid line connected to said first selector valve,

a second automatic control fluid line and a second manual control fluid line connected to said second selector valve,

automatic control pressure fluid supply and return lines,

a four-way manually closed control valve interposed between said automatic fluid supply and return lines and said first and second automatic control fluid lines,

a valve actuator operative in one direction from a normal neutral position to move said automatic control valve and to connect said automatic supply and first fluid lines and said automatic return and second fluid lines and in the other direction to connect said automatic supply and second fluid flow lines and said automatic return and first fluid flow lines,

said valve actuator being adapted to engage an elongated reference member disposed along the path to be traveled by said scraper,

manual control pressure fluid supply and return lines,

a manual control normally closed valve interposed between said manual control supply and return lines and said first and second manual control lines,

a manually operated valve actuating element operative in one position to move said manual control valve and connect said manual supply and first manual control fluid lines and said manual return and second manual control fluid lines and in an other position to connect said manual supply and second manual control fluid lines and said manual return and first manual control fluid lines,

said selector valves each being moveable in one position into communication with said manual fluid lines and in another position into communication with said automatic fluids lines, and

means interlocking said manually operated valve actuating element and said selector valves to move said selector valves to said another position only when said manually operated valve is moved to its normal closed position. 

1. A blade loading scraper comprising: a main frame, an earth working blade supported on said frame, rear traction means supporting the rear portion of said frame, a yoke having a pair of rearwardly extending side arms pivotally connected to an intermediate portion of said frame, front traction means supporting the forward end of said yoke, a double acting hydraulic ram connected between the intermediate portion of said yoke and the forward portion of said frame for controlling the elevation of said main frame, first and second flow lines communicating with opposite ends of said hydraulic ram, first and second three-way selector valves in continuous communication with said first and second flow lines respectively, a first automatic control fluid line and a first manual control fluid line connected to said first selector valve, a second automatic control fluid line and a second manual control fluid line connected to said second selector valve, automatic control pressure fluid supply and return lines, a four-way manually closed control valve interposed between said automatic fluid supply and return lines and said first and second automatic control fluid lines, a valve actuator operative in one direction from a normal neutral position to move said automatic control valve and to connect said automatic supply and first fluid lines and said automatic return and second fluid lines and in the other direction to connect said automatic supply and second fluid flow lines and said automatic return and first fluid flow lines, said valve actuator being adapted to engage an elongated reference member disposed along the path to be traveled by said scraper, manual control pressure fluid supply and return lines, a manual control normally closed valve interposed between said manual control supply and return lines and said first and second manual control lines, a manually operated valve actuating element operative in one position to move said manual control valve and connect said manual supply and first manual control fluid lines and said manual return and second manual control fluid lines and in an other position to connect said manual supply and second manual control fluid lines and said manual return and first manual control fluid lines, said selector valves each being moveable in one position into communication with said manual fluid lines and in another position into communication with said automatic fluids lines, and means interlocking said manually operated valve actuating element and said selector valves to move said selector valves to said another position only when said manually operated valve is moved to its normal closed position. 